At first , I measured standard port timing.Modify of intake portI don't change the output of high rotations, then I don't change exhaust timing .
Port name Open angle Closed angle Port opening position Exhaust port ATDC 85.5 degrees ATDC 275.0 degree From 26.6mm to 50.8mm The 1st scavenge port ATDC 119.0 degree ATDC 241.0 degree From 40.0mm to 52.2mm The 2nd scavenge port ATDC 119.7 degree ATDC 240.3 degree From 40.3mm to 53.2mm The 3rd scavenge port ATDC 120.0 degree ATDC 240.0 degree From 40.7mm to 53.3mm The 4th scavenge port ATDC 121.9 degree ATDC 238.1 degree From 41.0mm to 57.0mm
A scavenge port is late for going to the opposite side of an exhaust gas, .
It lookked like that made the thing for which timing is shifted consciously ,then I don't change scavenge timing.
There is level difference between the inner valve sheet of a rotary disk valve, and crank case outer valve sheet.Modify of scavenge port
I had seen the final type of RG gamma (factory racer that it has square 4 engine , code name is XR70), it didn't have level difference.
I modified it.
(It will become large if a picture is clicked)
There is no level difference between crank case and cylinder , and the rib of the port entrance was beautiful , and port size don't extend and change angle.Modify of exhaust port
However, There are level difference between cylinder and sleeve in the blow-off part of cylinder, then, I modified it.
(It will become large if a picture is clicked)
The top end of standard exhaust port has a little R , doesn't have holizontal straight line.The Exchanged parts of this time I exchanged article of consumption and all bearings.
If the exhaust port has holizontal straight line , it is enabled to lower the pressure in a cylinder quickly , and as a result scavenge is smooth.
I modified that the top end of standard exhaust port become horizontal straight line like a solid line from a dotted line, as shown in the following figure.Although the course of an exhaust port has a little rising at the middle. 
Moreover, there is a level difference between cylinder and sleeve.
Then, I modified those. the exhaust device was also deleted so that gas might flow smoothly ,when it changed into a full open state.
(It will become large if a picture is clicked)
There is a level difference between cylinder and pipe , then I modified it , too.
Return to back Return to top page
Fig.No. Index.No. Parts No. Description Quantity Note 2 22 09283-16002 Oil seal 4 5 16 17470-14100 Seal,Water pump shaft 1 New parts number;17470-46A01 5 22 09262-12003 Bearing 12x24x6 1 New parts number;08113-69010 5 23 09283-10005 Oil seal 10x20x5 1 6 12 09262-25007 Bearing 4 6 20 12151-14100 Pin,Piston 4 6 21 09263-14019 Bearing 4 6 23 09381-14001 Snap ring 8 8 21 13370-11301 Valve assy,Neadle 4 13 3 09263-30016 Bearing 1 New parts number;09263-30016 13 20 09263-15003 Bearing 15x28x2 1 13 21 09285-10002 Oil seal 10x17x5 1 14 12 09267-25002 Bearing 1 14 13 08110-62030 Bearing 1 14 26 09262-20078 Bearing 1 New parts number;08170-62040 14 27 08113-63050 Bearing 1 New parts number;09262-25073 15 8 09262-22012 Bearing 22×56×16 1 New parts number;09262-22025 15 9 09262-22018 Bearing 22x50x4 1 15 10 09263-22042 Bering 1 15 11 09283-22014 Oil seal 22x33x7 1 16 22 25522-20A00 Guide,Shift shaft 1 16 25 09285-12002 Oil seal 12x22x9 1 17 10 09283-20031 Oil seal 20x27x5 1
